As shown in FIG. 8, so-called sliding roof type, canvas top type or open roof type vehicles (hereinafter referred to as a sliding roof type vehicle) 100 are well known, which have an opening section 111 on a roof 110, and the opening section 111 is covered with a cover member 120 which can be opened and closed. This conventional sliding roof type vehicle 100 is typically has slide rails 111b provided along both left and right sides of the opening section 111 on the roof 110, and along the slide rails 111b, a plurality of slide members supporting both edges of the cover member 120 are provided slidably in the front-and-rear direction of a vehicle. A plurality of slide members is provided in a longitudinal direction at the pre-determined distance on both edges of the cover member 120.
Depending upon passengers' mood or weather or temperature, the opening section 111 on the roof 110 is closed by moving each slide member and extending the cover member 120 forward along the slide rails 111b. Conversely, the roof 110 is opened when the cover member 120 is folded at a rear edge of the opening section 111, or rolled and wound up by moving backward each slide member along the slide rails 111b. 
However, with such a sliding roof type structure, the folded cover member 120 closes a part of a rear edge of the opening section 111, that is, by length L1 in the longitudinal direction, and swells upward from the roof 110. Therefore, since the opening section 111 of the roof 110 has length L2 shorter by L1 than the total length L in its longitudinal direction, the open area of the opening section 111 of the roof 110 is smaller and its appearance is also deteriorated. When also a rear window 112 is opened, a rear edge 110a of the roof 110 and the folded cover member 120 are placed between an opening section of the rear window 112 and the opening section 111 of the roof 110. Thereby, feeling of openness is spoiled when a rear window 112 is opened.
JP 2005-313737 A discloses a vehicle roof storage structure wherein a storage space for a roof constituting member is provided behind a vehicle seat. The roof constituting member is stored in a package tray that is rotated by a rotating mechanism to store the roof constituting member into the storage space.
JP 2002-046473 A discloses a convertible vehicle roof wherein a front portion and a rear portion of the roof are movably supported on a vehicle body. The front and the rear portions of the roof are stored in a roof storage room. The front portion of the roof is swung when descending into the roof storage room by a swing supporting device, and stored diagonally or substantially vertically.
JP 2003-507244 A (corresponding to WO01/014157) discloses a detachable covering module in a passenger space of a vehicle and a vehicle provided with it wherein a cassette composing a slidable rear window along an arch-shaped roof side panel and a foldable flexible roof device on the cassette are supported.
In the roof storage structure disclosed in said JP 2005-313737 A, the storage space for a roof constituting member is relatively large, and especially long in the front-and-rear direction, causing a luggage space extremely small damaging convenience.
In the convertible vehicle roof disclosed in JP 2002-046473 A, similarly to the roof storage structure disclosed in said JP 2005-313737 A, the roof storage space is large, similarly causing a luggage space small damaging convenience.
In the detachable covering module in a passenger space of a vehicle disclosed in JP 2003-507244 A (corresponding to WO01/014157), the cassette composing a rear window and a flexible roof device slide along a roof side panel and stored inside a storage under a trunk floor. However, the covering module has a complex structure, and it is necessary upon storage to open a rear hutch, pull out a trunk floor backward, and introduce the cassette and the flexible roof device into the storage space. Therefore, complex operation is required for storage, and it is difficult, for example, to store or develop a roof while a driver or passengers stay in a vehicle.
Referring to the above-mentioned problems, the object of the present invention is to provide a storage structure for a cover member of a sliding roof type vehicle wherein a luggage space is not so small, a cover member constituting a roof is folded and stored, and a large opening area is maintained in a roof upon cover member storage.